This program project is devoted to the mechanisms of pulmonary ventilation and bloodflow, and the relationsips between ventilation, bloodflow and pulmonary gas exchange. Mechanisms of ventilation are being investigated during high frequency mechanical ventilation, during changes in gravitational loading, and in patients with asthma and other types of lung disease. Control of pulmonary bloodflow is being investigated during alveolar hypoxia, lung edema, and at different stages of lung inflation. Pulmonary gas exchange is being studied in patients with various types of lung disease, in diving mammals, in the avian lung, and in theoretical models in which ventilation and bloodflow are mismatched.